Memory is often implemented in electronic systems, such as computers, cell phones, hand-held devices, etc. There are many different types of memory, including volatile and non-volatile memory. Volatile memory may require power to maintain its data and may include random-access memory (RAM), dynamic random-access memory (DRAM), static random-access memory (SRAM), and synchronous dynamic random-access memory (SDRAM). Non-volatile memory may provide persistent data by retaining stored data when not powered and may include NAND flash memory, NOR flash memory, nitride read only memory (NROM), phase-change memory (e.g., phase-change random access memory), resistive memory (e.g., resistive random-access memory), or the like. Hard disc drives (HDDs) may be an example of another type of memory and may include magnetic tapes and/or optical discs.
Flash memory, may, for example, use one-transistor memory cells. Changes in threshold voltage of the cells, through programming (which is sometimes referred to as writing) of charge-storage structures (e.g., floating gates or charge traps) or other physical phenomena (e.g., phase change or polarization), may determine the data value of each cell.
In some examples, a NAND flash memory may include groups (e.g., strings) of series-coupled (e.g., one-transistor) non-volatile memory cells. The series-coupled memory cells in a string, for example, may be between a data line (e.g., a bit line) and a source. For example, the memory cells in a string may be coupled in series source to drain. Memory cells at specific locations in the strings, for example, may be commonly coupled to an access line, such as a word line.
Some NROMs, for example, may store a charge in a nitride, for example. The nitride, for example, might be part of an oxide-nitride-oxide (ONO) gate dielectric. In some examples, NROM cells may be n-channel field-effect transistors, such as n-FETs, where the gate dielectric may be replaced by an ONO stack.